As catalysts that are useful for cyanhydrin hydration and exhibit high activity and high selectivity, various catalysts composed mainly of manganese oxides have been disclosed together with production processes for such catalysts (see, for example, Patent Documents 1 to 8). However, these catalysts are still problematic in that when they are used industrially, their structures are insufficient in physical strength, and hence collapse or pulverization of the catalysts are caused, inevitably resulting in increase of pressure loss and concomitant degradation of productivity so as to disturb continuation of operation.
Patent Document 1: Japanese Patent Laid-Open No. 63-57534
Patent Document 2: Japanese Patent Laid-Open No. 63-57535
Patent Document 3: Japanese Patent Laid-Open No. 3-68447
Patent Document 4: Japanese Patent Laid-Open No. 3-93761
Patent Document 5: Japanese Patent Laid-Open No. 5-170720
Patent Document 6: Japanese Patent Laid-Open No. 6-269666
Patent Document 7: Japanese Patent Laid-Open No. 9-19637
Patent Document 8: Japanese Patent Laid-Open No. 9